JPS6057384B2 - Application method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuously running belt-shaped support (hereinafter referred to as ゛-゛↓←゛A-A$F11). The present invention relates to a method of applying a coating liquid to a supported web.

Conventionally, when applying a coating liquid to a continuously running web, the side of the web that is not coated (hereinafter referred to as the "back side of the web") is used.

) was commonly applied to the web while supporting it in contact with a rigid roller. However, in this method, foreign matter attached to the back surface of one web or the surface of the rigid roller temporarily narrows the distance between the web and the coating device, and the uniformity of the distance between the coating device and the web affects the uniformity of coating. When applying coating methods such as heat coat method, extrusion coat method, doctor coat method, etc., the distance between the two coating devices and the web tends to cause uneven spots on the coated surface. In coating methods that require uniformity of coating, it is necessary to maintain the spacing accuracy between the coating device and the web on the μ order, and high precision is required in the coating device, rigid roller, web thickness, etc. . There were problems such as slipping between the No. 31 web and the rigid roller due to various disturbances, and scratches were likely to occur on the back surface of the web, and the results were not necessarily satisfactory. Therefore, a method has been proposed and approved in which the web is supported by a gate in the fluid and coated without using a rigid roller. Such experimental findings can be demonstrated theoretically as shown below.

In the curtain application method, the height of the curtain is
ft], the curtain film thickness and δ[G] at the time of collision between the curtain and the web, and the falling velocity of the coating liquid at the time of collision, UccC! R/Sec], the relative speed between the coating liquid and the web at the time of collision is UcwCcm/Sec], the running speed of the web is UwcCl/Sec], and the amount of coating liquid applied is ECcc/i].

These quantities vary due to fluctuations in web floating, so
Let the average values be 100, τ, 2, ■Cw, 2W, and 100, respectively, and the fluctuations of these quantities are Δh1Δδ)−
Letting ΔUClΔUCWlΔUWlΔE, it can be expressed as ΔUClΔUCWlΔUWlΔE. Also, if α is a constant of proportionality, then if we insert the above relationship into this and ignore higher-order quantities, we get
~-Yo-VVl▼1V-VV adventure! Therefore, the rate of variation in coating amount, which indicates the degree of coating unevenness, can be expressed as shown in the following equation.

-Here, the web floating fluctuation amount Δh (ACC7R): Half amplitude, ω [1/Sec]
: angular velocity, FO/Sec] : frequency). Also, assuming that the coating liquid flows down according to free fall, and assuming that the average position of the web does not change, then Ucw = U
If c'Ufcw=J2gi and β is the liquid supply amount per unit width [CC/d・Sec], this is a constant, so 1=β/Jkg hill, Δδ=-(β/JkgW) (Δh/2W).゜． ΔE/
100=AωCOsO)t/12gK−A sinωt/tai
Self 0 = Tan-1 (ω2/Koioka)/(1/4W Fuichia?
÷: Curtain height h≧5C, which is usually adopted in the curtain coating method! Under the condition of n, in the web flying fluctuation frequency range f=lν>10Hz, which is usually a problem, under such conditions, (L[ji/C)111CLΔ211Wl ku66■, and the coating amount is The result is that the variation in is inversely proportional to the impingement velocity of the coating liquid on the web.

The above theoretical formula was derived based on the assumption that a thin film of coating liquid collides with the web due to free fall in the curtain coating method, but these assumptions have been satisfied experimentally and are widely used in curtain coating. This may fall under the method.

Furthermore, it is clear that the above theoretical formula holds true not only in the case of free fall, but also in the case where the coating liquid is made into a thin film and collides with the web. It can be said that it has been demonstrated that coating unevenness can be suppressed to a permissible value or less when collisions occur.

For example, when spraying a thin film of coating liquid horizontally under pressure from a slit-shaped nozzle, in the above equation, instead of c=12gW, the spraying speed of the coating liquid from the nozzle US= q/d (d: Nozzle slit gap [c
! n)), and in this case, (ΔE/100) M
ax=A゛ω(q/d). To explain more specifically using a photographic material as an example, when a relatively high frequency coating film thickness unevenness of 1 to 0.5% occurs in a photographic material, it becomes a horizontal step-like unevenness. This often causes fatal defects in the product, but when using the curtain coating method, the amount of web flying fluctuation that causes such coating unevenness is smaller than when using conventional bead coating methods, doctor coating methods, etc. It has been experimentally and theoretically confirmed that this is extremely large, usually more than 1@, and that the coating method according to the present invention does not cause horizontal step-like coating unevenness even in response to larger fluctuations in web flying. It is recognized that it is difficult.

As described above, according to the method of the present invention in which the coating liquid is formed into a thin film and is applied by colliding with the web at a speed higher than a certain level, the disadvantages of fluid support can be eliminated and the advantages can be fully realized. It can be seen that it is possible to perform effectively.

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a schematic cross-sectional view of a coating device showing an embodiment of the present invention.

In FIG. 1, a web 1 is continuously moved while being supported by fluid blown out from a nozzle 3 of a cylindrical fluid blowing device 2. As shown in FIG. Cylindrical fluid blowing device 2
The fluid supply to the pump is carried out by commonly used means such as a blower or a pump, but these are not shown in FIG. The extrusion type liquid injector 4 is provided above the web 1 at a considerable distance from the web 1, and the coating liquid 5 is supplied to the extrusion type liquid injector 4 by a supply means (not shown) such as a metering pump. The liquid is extruded into a thin film through the slit 6 by the extrusion type injector 4 to form a curtain 7. The curtain 7 made of the coating liquid 5 falls freely and collides with the surface of the web 1 running across the curtain 7, so that a coating film 8 made of the coating liquid 5 is formed on the web 1. Here,
The running direction of the web 1, the position of the collision part between the web 1 and the curtain 7, the range of the fluid support part, etc. can be arbitrarily determined to some extent by taking into consideration the spatial relationship with the surrounding devices, but if the web 1 is a cylindrical fluid Since the floating fluctuation of the web 1 is relatively large at a portion away from the fluid support portion by the blowing device 2,
It is not preferable to cause the curtain 7 to collide with the web 1 and apply the coating at such a position. Also, Web 1 and Curtain・
If the angle formed on the upstream side of the curtain 7 with the curtain 7 is an obtuse angle, especially if it exceeds 100 degrees, the direction of the coating liquid 5 is abruptly changed during coating, resulting in disturbances such as the formation of liquid pools. This is undesirable because the coating itself becomes unstable or uneven coating occurs (1). FIG. 2 is a schematic cross-sectional view of a coating device showing another embodiment of the present invention.

In FIG. 2, the web 1 is fluidly supported by fluid blown out from a cylindrical fluid blowing device 2,
Coating liquid 5 is caused to collide with the surface in the form of a thin film-like jet stream from an extrusion type liquid injector 4 provided on the side surface of the cylindrical fluid blowing device 2, thereby performing coating. In this embodiment, the collision velocity is not accelerated by gravity, so
In order to obtain a collision speed that does not cause uneven coating, the gap between the slits 6 of the extrusion type liquid pourer 4 must be made sufficiently narrow. It goes without saying that the present invention is not limited to the embodiments described above, and that various modifications can be made.

For example, instead of letting a thin coating liquid fall freely,
When ejecting as a jet toward the web at a speed higher than a certain speed, it is not necessarily necessary to eject in a horizontal direction, and various angles such as upward, diagonally upward, etc. can be selected.

The present invention is not limited to so-called single-layer coating, but can also be applied to so-called simultaneous multi-layer coating, in which two or more coating solutions are simultaneously coated in a multilayer relationship.

In such cases, the special public interest law concerning curtain coating
As is clear from No. 24133, two or more types of coating liquids are overlapped in advance in a face-to-face relationship to form a thin film, and this thin film coating liquid is applied by colliding with the web at a speed higher than a certain level. preferable. Any fluid support method that can be used in the present invention can be used as long as static pressure can be stably maintained between the web and the web. for example,
Fluids disclosed in Japanese Patent Publication Nos. 49-17853, 49-44108, 50-19130, 51-38737, U.S. Patent No. 3,635,192, U.S. Patent No. 3,688,7, etc. All of the support methods are used as the fluid support method of the present invention. It is possible. The present invention is not limited to coating liquids for photographic light-sensitive materials, but can be widely applied to coating liquids for pressure-sensitive copying paper, magnetic coating liquids, and the like.

It is particularly preferably applied to applications that require a relatively precise coating film. In the curtain coating method of the present invention, various devices disclosed in Japanese Patent Publications No. 49-1413@, No. 49-241, No. 49-3-47, and No. 76151/1983 can be applied. I can do it. For example, as a liquid injector, both a so-called slide type liquid injector and an extrusion Z type liquid injector can be used, and in order to stabilize the curtain, a guide rod may be used or an air shield may be provided. This brings about favorable results.
Further, many of the various conditions disclosed in these documents, such as curtain height and flow rate, are also applicable to the present invention. Ta~
However, it goes without saying that the selection should be made carefully depending on the physical properties of the target coating liquid. When the present invention is used in the production of photographic light-sensitive materials, the manufacturing method, composition, necessary additives, web material, various treatments, etc. of the photographic coating solution shall be
9-1413 Eel, No. 47-241, No. 49-354
All the materials disclosed in No. 47 can be used.

The photographic coating solution here includes not only photosensitive ones such as photographic emulsions, but also all kinds of coating solutions used in the production of photographic light-sensitive materials, such as undercoat coating solutions, anti-halation coating solutions, and back layer coating solutions. included. When the present invention is used in the production of magnetic recording materials, a method for producing a coating liquid for magnetic/magnetic recording materials;
The composition, necessary additives, web material, various treatments, etc.
All the materials disclosed in Japanese Patent Application No. 51-154491 can be used.

Here, as the coating liquid for magnetic recording material, magnetic coating liquid,
This includes all coating liquids used in the production of magnetic recording materials, such as coating liquids for back coats.In addition, when the curtain coating method according to the present invention is applied to the production of magnetic recording materials, an orientation device is attached to the free-falling curtain portion. It is necessary to set implementation conditions specific to the magnetic recording material and the isomagnetic coating liquid that improves the orientation and the stability of the curtain film. When the present invention is used in the production of pressure-sensitive copying paper, the manufacturing method, composition, necessary additives, web material, various treatments, etc. of the coating liquid for pressure-sensitive copying paper can be used. All the coating liquids disclosed in Japanese Patent Application No. 76743/1988 can be used.As coating liquids for pressure-sensitive copying paper, coating liquids containing microcapsules as a main component, and coating liquids containing a color developer as a main component can be used. It includes all coating liquids used in the manufacture of pressure-sensitive copying paper, such as coating liquids as components.In addition, when the curtain coating method according to the present invention is applied to the manufacture of pressure-sensitive copying paper, coating liquids for pressure-sensitive copying paper are included. Although it is necessary to set operating conditions specific to the liquid, the conditions disclosed in Japanese Patent Application No. 76743/1988 can be used for this purpose.

Furthermore, in the present invention, fluid includes both gas and liquid.

The gas is not particularly limited as long as it does not have a harmful effect such as reacting with the coating liquid or other substances such as air, nitrogen, helium, carbon dioxide, etc., and is not dangerous to handle, but from the point of view of cost. Considering, air is the most common. Water is the most common fluid, but when supporting the web with a liquid, it is especially important to
Effects on the web surface due to coating, cleaning, etc. It is necessary to consider the impact and collection method. In the present invention,
When the coating liquid in the form of a thin film is caused to collide with the web, the collision speed needs to be at least a certain value. As is clear from the above-mentioned theoretical explanation, the lower limit value of this collision speed is limited by changes in the web's flying height, the degree of movement, etc., and it is difficult to unconditionally state an appropriate value. On the other hand, if the collision speed is too high, depending on the physical properties of the coating liquid, coating conditions, etc., pooling of the coating liquid may occur at the time of collision, resulting in uneven coating, or if the curtain coating method is used, the curtain may The height of the curtain film must be made extremely high, and it has been recognized that undesirable phenomena such as fluctuations in the curtain film and extreme thinning of the curtain film at the bottom of the curtain film may cause the curtain film to become unstable. - It is not desirable. Therefore, in reality, the collision speed is required to be below a certain value. However, the upper limit of this collision speed depends on the physical properties of the coating liquid, coating conditions, etc., and under the physical properties of the coating liquid and coating conditions that are normally used, the collision velocity rarely exceeds this upper limit. Therefore, it can be said that the upper limit value is not really a problem in practice. As mentioned above, the value of the collision velocity should actually be determined experimentally, but is usually 0.5 to 37 n/sec, preferably 1 to 2.5 TrL/sec, and more preferably 1.5 to 37 n/sec.
It is appropriate to set it to 2 wL/sec. According to the present invention, it is possible to use a fluid support method without causing horizontal step-like coating unevenness. Precision machining of
It becomes possible to realize good coating.

Examples will be given below to clearly demonstrate the effects of the present invention. Example 1 Width 1100m1 Thickness 1 running continuously at 60m/min
A polyethylene terephthalate film of 80μ was heated at 20℃ using a cylindrical air blowing device with a diameter of 1200Ti1.
Blow out the air of
The coating solution having the composition shown in Table 1 was applied at a coating width of 1000 m1 and a coating amount of 80 cc/by using a curtain coating method with the curtain height set to 15 cm while supporting the sample at a width of 0 m.

When the coating film obtained by rapidly solidifying and drying after coating was inspected, the film thickness distribution was substantially uniform, and no coating unevenness was observed even when inspected using reflected light and transmitted light.

Example 2 The same conditions as Example 1, only the coating speed was 120 m.
When coating was carried out at a different speed of 1/min, the coating film after drying was as good as in Example 1 with no uneven coating.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views of a coating device showing an embodiment of the present invention. 1...Web, 2...Cylindrical fluid blowing device, 3...Nozzle, 4...Extrusion type liquid injection device, 5...・Coating liquid, 6...Slit, 7...Curtain, 8...Coating film.

Claims (1)

[Scope of Claims] 1. A method of applying a coating liquid to the back side of a continuously running web while supporting it with a fluid, in which at least one type of coating liquid in the form of a thin film collides with the web at a speed higher than a certain level. A coating method characterized by applying the product at least once. 2. The coating method according to claim 1, wherein the coating solution is applied by colliding with the web at a collision speed of 0.5 m/sec to 3 m/sec. 3 Forming a free-falling curtain consisting of a thin film coating liquid,
3. The coating method according to claim 1, wherein the coating is carried out by colliding the free-falling curtain with the web. 4. The coating method according to any one of claims 1 to 3, wherein the coating liquid is a photographic coating liquid. 5. The coating method according to any one of claims 1 to 3, wherein the coating liquid is a coating liquid for magnetic recording materials. 6. The coating method according to any one of claims 1 to 3, wherein the coating liquid is a coating liquid for pressure-sensitive copying paper.